The present invention relates to a method and a device for controlling a motion sequence of a machine element. Many branches of industry, e.g., the packaging industry or the textile industry, use manufacturing machines that often include a large number of movable machine elements, the motions of which are precisely coordinated with one another. In modern systems, it is common to control the motion sequences of these individual machine processes using processors or control devices, the motion sequences to be carried out being programmed in these control devices.
For instance, position values of a master element and/or a master shaft, and the position data for a slave element and/or a slave shaft assigned thereto, may be stored in a control device.
The method according to the present invention may be used, e.g., in packaging machines, printing presses, textile machines, and automation systems. It would also be possible to use the method in systems that are controlled electrically, hydraulically, and pneumatically. The present invention may also be used in other systems in which the motion of several machine elements are to be coordinated with one another. In this coordination process, it is often necessary to also consider basic conditions in the section in which the motion is carried out, i.e., an initial speed and an end speed, a starting position and an end position, and an initial and final acceleration must be taken into consideration in particular. In the related art, functional relationships in the form of higher-order polynomials are typically used to control these motion sequences exactly. With the aid of these polynomials, a master shaft position is related to the assigned slave-shaft position.
By using these polynomials, e.g., fifth-order polynomials, the relationship may be defined, in particular with consideration for the basic conditions described above. Cases may occur, however, in particular when unfavorable, normalized boundary values for speed are involved, in which the polynomial “overshoots”, that is, e.g., the position of the machine element to be controlled slides into the negative range and/or a backward motion takes place. Backward motions of this type are fatal in many industries, e.g., the printing industry, and are therefore unacceptable.
US 2006/0167570 A1 describes a method for the rapid control of a process variable without overshoot, with which a polynomial function is used and feedback is taken into consideration. A controller is therefore disclosed in this publication, it being necessary to always use the data from an appropriate sensor in the control process.